1. Field of the Invention
The present invention relates to a flash device which can adjust the flash coverage or luminous intensity distribution characteristic in accordance with, e.g., the focal length of a zoom lens in use.
2. Description of the Related Art
FIGS. 8A and 8B show a typical (conventional) zoom flash device 100. The zoom flash device 100 has a flash tube 50, a lens 52 and a reflector 54. One of the lens 52 and the reflector 54 is moved relative to the other along an optical axis of the zoom flash device 100 to change the space between the lens 52 and the reflector 54 to adjust the flash coverage (luminous intensity distribution) in accordance with the focal length (angle of view) of a zoom lens (not shown).
The structure of such a conventional zoom flash device is unfavorable with respect to the recent tendency of miniaturization of cameras because a sufficient space allowing one of the lens 52 and the reflector 54 to move relative to the other needs to be provided between lens 52 and the reflector 54.
In addition, if such a space between the lens 52 and the reflector 54 is large, vignetting occurs. Namely, a portion of the flash light reflected by the reflector 54 is obstructed by the edge of the aperture of the lens 52, thus not exiting out of an exit surface (front surface) of the lens 52. This problem of vignetting is noticeable, especially with the marginal rays of flash light that pass through the perimeter of the lens 52, thus causing a reduction in luminous intensity of the marginal rays of flash light.
The present invention provides a flash device which can adjust the flash coverage without changing the space between the lens and the reflector with a minimum reduction in luminous intensity of the marginal rays of flash light. Other aspects and advantages of the present invention will become apparent to one skilled in the art by reading the following disclosure and the appended claims.
According to an aspect of the present invention, a flash device is provided, including a flash tube; a reflector having a first reflector portion and a second reflector portion which are arranged symmetrically with respect to a plane including an axis of the flash tube, a space between the first reflector portion and the second reflector portion increasing in a direction toward a front end aperture of the reflector; and a lens positioned so as to be opposed to the front end aperture of the reflector. At least a part of the first reflector portion on a side of said front end aperture and at least a part of the second reflector portion on a side of said front end aperture are interlocked with each other to be movable in opposite directions along a direction perpendicular to the plane.
It is desirable for the part of the first reflector portion and the part of the second reflector portion to parallel-translate in the opposite directions.
It is desirable for the first reflector portion to include a first rear stationary reflector and a first front movable reflector. The second reflector portion includes a second rear stationary reflector and a second front movable reflector. The first front movable reflector and the second front movable reflector are interlocked with each other to be movable in the opposite directions along the direction perpendicular to the plane. The first and second front movable reflectors parallel-translate in the opposite directions.
The reflector can include two end reflector plate portions positioned at opposite ends of the flash tube, respective front ends of the two end reflector plate portions, the first reflector portion and the second reflector portion forming a substantially rectangular front end aperture of the reflector.
The present disclosure relates to subject matter contained in Japanese Patent Application No. 2002-189156 (filed on Jun. 28, 2002) which is expressly incorporated herein by reference in its entirety.